1. Field of the Invention
This invention relates to devices for obtaining percutaneous access in intra-arterial and intravenous therapy in medicine. More particularly, this invention relates to intravascular sheaths and methods for percutaneous insertion of such sheaths.
2. Description of the Background Art
The use of intra-arterial and intravenous therapy in medicine has revolutionized therapy both in terms of administration of drugs and fluids and also the use of therapeutic devices placed in remote portions of the body from percutaneous access. Devices to obtain percutaneous access has traditionally involved metal or plastic sheaths which remained in dwelling after percutaneous puncture of the appropriate vessel through the skin. These devices could either be withdrawn after therapy was complete or left in dwelling for many days. The placement of the sheath is done by a skilled operator. The following describes three of the more common methods for sheath placement.
One of the older methods for placement of intravascular sheaths employs a sheath that is tightly wrapped over a steel needle. The needle is placed through the skin and into a vein. A sheath is then advanced over the needle into the vein. Once in place, the needle is withdrawn leaving the sheath in the desired position in the vein.
Another method also employs the use of a hypodermic needle to puncture the skin. The needle is then inserted into the desired vein. A plastic tube is inserted within the inner hollow core of the needle and advanced until the tube enters the vein. The needle is then withdrawn from the vein in the skin, leaving the tubing within the vein.
Finally, the third method for placement of intravascular sheaths is commonly known as the "Seldinger"technique. As before, the Seldinger technique employs the use of a hypodermic needle to puncture the skin and enter the desired vein. A metal guide wire is inserted within the inner hollow core of the needle and then advanced through the needle into the vein. The needle is then removed. A hollow core introducer, usually made of plastic over which a sheath is tightly wrapped, is placed over the metal wire and advanced along the length of the wire to dilate the skin, vein wall and lumen of the vein and to "introduce" the sheath therein. The sheath is then slightly advanced over the introducer a the introducer and the metal guide wire are removed, leaving only the sheath within the vein.
Each of the methods for arterial catherization have enjoined various degrees of popularity; however disadvantages are associated with each. Specifically the second method referenced above in which a plastic tube is inserted within the hollow core of the needle, has the disastrous potential of inadvertently shearing off the plastic tube on the sharp edge of the needle. Thus, it is more common to utilize either the first or third methods referenced above in which the sheath is inserted over the needle or over a dilator/introducer. Unfortunately, both of these methods commonly present a problem of the sheath edge being caught by the subcutaneous tissue or the muscular tissue making up the arterial wall. Once the edge is caught, a kink is formed in the sheath, rendering further entry into the vein either impossible or at best difficult. Furthermore, the risk of injury or trauma to the vein is significantly increased.
Therefore, it is an object of this invention to provide an apparatus which overcomes the aforementioned inadequacies of the prior art devices and provides an improvement which is a significant contribution to the advancement of the sheath introducer art.
Another object of this invention is to provide a sheath introducer apparatus and method which minimizes risk of the sheath edge being caught by the subcutaneous tissue or the muscular tissue making up the arterial wall, thereby minimizing kinking or other damage to the sheath which in turn minimizes trauma of the subcutaneous tissues and arterial walls from a kinked sheath.
Another object of this invention is to provide a sheath introducer apparatus and method which does not employ the insertion of a tube within a hypodermic needle that could otherwise run the risk of shearing off the plastic tube on the sharp edge of the needle.
Another object of this invention is to provide a sheath introducer apparatus and method which allows more force to be applied to the introducer without damage to its sheath thereby making access through scarred tissue easier while minimizing damage to the sheath.
Another object of this invention is to provide a sheath introducer apparatus and method including a sheath which is expandable along its longitudinal length, allowing devices which are larger than the inner diameter of the collapsed sheath, to be utilized.
The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.